diff --git a/src/main/java/graphql/schema/GraphQLSchema.java b/src/main/java/graphql/schema/GraphQLSchema.java
index e365ef774b..e7026ad6c3 100644
--- a/src/main/java/graphql/schema/GraphQLSchema.java
+++ b/src/main/java/graphql/schema/GraphQLSchema.java
@@ -71,7 +71,7 @@ public class GraphQLSchema {
     private final ImmutableMap<String, ImmutableList<String>> interfaceNameToObjectTypeNames;
 
     /*
-     * This constructs partial GraphQL schema object which has has the schema (query / mutation / subscription) trees
+     * This constructs partial GraphQL schema object which has the schema (query / mutation / subscription) trees
      * in it but it does not have the collected types, code registry nor the type references replaced
      *
      * But it can be traversed to discover all that and filled out later via another constructor.
@@ -104,7 +104,7 @@ private GraphQLSchema(Builder builder) {
     }
 
     /*
-     * This constructs a full fledged graphql schema object that has not yet had its type references replaced
+     * This constructs a fully fledged graphql schema object that has not yet had its type references replaced
      * but it's otherwise complete
      */
     @Internal
@@ -255,7 +255,7 @@ public <T extends GraphQLType> List<T> getTypes(Collection<String> typeNames) {
 
     /**
      * Gets the named type from the schema or null if it's not present.
-     *
+     * <p>
      * Warning - you are inviting class cast errors if the types are not what you expect.
      *
      * @param typeName the name of the type to retrieve
@@ -286,7 +286,7 @@ public boolean containsType(String typeName) {
      *
      * @return a graphql object type or null if there is one
      *
-     * @throws graphql.GraphQLException if the type is NOT a object type
+     * @throws graphql.GraphQLException if the type is NOT an object type
      */
     public GraphQLObjectType getObjectType(String typeName) {
         GraphQLType graphQLType = typeMap.get(typeName);
@@ -433,14 +433,14 @@ public List<GraphQLDirective> getDirectives() {
     }
 
     /**
-     * @return a map of non repeatable directives by directive name
+     * @return a map of non-repeatable directives by directive name
      */
     public Map<String, GraphQLDirective> getDirectivesByName() {
         return directiveDefinitionsHolder.getDirectivesByName();
     }
 
     /**
-     * Returns a named directive that (for legacy reasons) will be only in the set of non repeatable directives
+     * Returns a named directive that (for legacy reasons) will be only in the set of non-repeatable directives
      *
      * @param directiveName the name of the directive to retrieve
      *
@@ -535,7 +535,7 @@ public List<GraphQLDirective> getSchemaDirectives(String directiveName) {
      * directives for all schema elements, whereas this is just for the schema
      * element itself
      *
-     * @return a map of directives
+     * @return a list of directives
      */
     public List<GraphQLAppliedDirective> getSchemaAppliedDirectives() {
         return schemaAppliedDirectivesHolder.getAppliedDirectives();
@@ -641,6 +641,7 @@ public static Builder newSchema(GraphQLSchema existingSchema) {
                 .query(existingSchema.getQueryType())
                 .mutation(existingSchema.getMutationType())
                 .subscription(existingSchema.getSubscriptionType())
+                .extensionDefinitions(existingSchema.getExtensionDefinitions())
                 .introspectionSchemaType(existingSchema.getIntrospectionSchemaType())
                 .codeRegistry(existingSchema.getCodeRegistry())
                 .clearAdditionalTypes()
@@ -873,8 +874,8 @@ public GraphQLSchema build(Set<GraphQLType> additionalTypes) {
         /**
          * Builds the schema
          *
-         * @param additionalTypes      - please don't use this any more
-         * @param additionalDirectives - please don't use this any more
+         * @param additionalTypes      - please don't use this anymore
+         * @param additionalDirectives - please don't use this anymore
          *
          * @return the built schema
          *
diff --git a/src/test/groovy/graphql/schema/GraphQLSchemaTest.groovy b/src/test/groovy/graphql/schema/GraphQLSchemaTest.groovy
index de2a51bf04..bf18e083c2 100644
--- a/src/test/groovy/graphql/schema/GraphQLSchemaTest.groovy
+++ b/src/test/groovy/graphql/schema/GraphQLSchemaTest.groovy
@@ -5,6 +5,8 @@ import graphql.Directives
 import graphql.ExecutionInput
 import graphql.GraphQL
 import graphql.TestUtil
+import graphql.language.Directive
+import graphql.language.SchemaExtensionDefinition
 import graphql.schema.idl.RuntimeWiring
 import graphql.schema.idl.TypeRuntimeWiring
 import graphql.util.TraversalControl
@@ -129,6 +131,23 @@ class GraphQLSchemaTest extends Specification {
                 ))
     }
 
+    def "schema builder copies extension definitions"() {
+        setup:
+        def schemaBuilder = basicSchemaBuilder()
+        def newDirective = Directive.newDirective().name("pizza").build()
+        def extension = SchemaExtensionDefinition.newSchemaExtensionDefinition().directive(newDirective).build()
+        def oldSchema = schemaBuilder.extensionDefinitions([extension]).build()
+
+        when:
+        def newSchema = GraphQLSchema.newSchema(oldSchema).build()
+
+        then:
+        oldSchema.extensionDefinitions.size() == 1
+        newSchema.extensionDefinitions.size() == 1
+        ((Directive) oldSchema.extensionDefinitions.first().getDirectives().first()).name == "pizza"
+        ((Directive) newSchema.extensionDefinitions.first().getDirectives().first()).name == "pizza"
+    }
+
     def "clear directives works as expected"() {
         setup:
         def schemaBuilder = basicSchemaBuilder()
@@ -233,10 +252,8 @@ class GraphQLSchemaTest extends Specification {
         }
             
         union UnionType = Cat | Dog
-            
         '''
 
-
         when:
         def schema = TestUtil.schema(sdl)